Method and a Device for Transferring Signalling Information in a Tdma Based System

ABSTRACT

A method and a device for transferring signalling information in a TDMA based system. Temporal alignment of values for a retransmission number parameter (R) with the TDMA frame structure is determined on the basis of which a first radio packet to be sent in a number of first TDMA frames is encoded by using a certain first value for the parameter and a second radio packet to be sent in a number of second TDMA frames is encoded by using a certain second value for the parameter. The first and second radio packets are transmitted to the recipient that adheres to the same temporal alignment rules and can thus properly decode both the packets. The solution can be utilized especially in GERAN radio access network with FLO (Flexible Layer One) for transferring signalling information on half-rate channels.

FIELD OF THE INVENTION

The present invention relates generally to communication systems. Inparticular the invention concerns GERAN (GSM/EDGE Radio Access Network)radio access network and air interface thereof in which a special typeof physical layer called flexible layer one (FLO) is utilized.

BACKGROUND OF THE INVENTION

Modern wireless communication systems such as GSM (Global System formobile communications) and UMTS (Universal Mobile TelecommunicationsSystem) are capable of transferring various types of data over the airinterface between the network elements such as a base station and amobile station (MS). As the general demand for transfer capacitycontinuously rises due to e.g. new multimedia services coming available,new more efficient techniques have been developed in order to exploitthe existing resources to a maximum extent.

A technical report [1] discloses a concept of flexible layer one, a newphysical layer proposed for the GERAN. The ingenuity of the conceptrelies on the fact that the configuration of the physical layerincluding e.g. channel coding and interleaving is specified not untilthe call set-up. Thus, the support of new services can be handledsmoothly without having to specify new coding configuration schemesseparately in connection with each release.

Development work of the FLO concept has been provided with somewhatstrict requirements. FLO should, for example, support multiplexing ofparallel data flows on to a basic physical subchannel and provideoptimisation of spectral efficiency through the support of differentinterleaving depths, unequal error protection/detection, reduced channelcoding rate granularity and support of different (8PSK, GMSK etc)modulations. Moreover, the solution shall be future proof and minimizethe overhead introduced by the radio protocol stack.

According to the GERAN Release 5 the MAC sublayer (Layer 2 for FLO)handles the mapping between the logical channels (traffic or control)and the basic physical subchannels introduced in [2].

In UTRAN (UMTS Radio Access Network), the MAC utilizes so-calledTransport Channels TrCH for transferring data flows with given QoS's(Quality of Service) over the air interface. As a result, severaltransport channels, that are configured at call set-up, can be active atthe same time and be multiplexed at the physical layer.

Now, by adopting the idea of FLO, aforesaid flexible transport channelscan be utilized in GERAN as well. Accordingly, the physical layer ofGERAN may offer one or several transport channels to the MAC sublayer.Each of these transport channels can carry one data flow providing acertain Quality of Service (QoS). A number of transport channels can bemultiplexed and sent on the same basic physical subchannel at the sametime.

The configuration of a transport channel i.e. the number of input bits,channel coding, interleaving etc. is denoted as a Transport Format (TF).Furthermore, a number of different transport formats can be associatedto a single transport channel. The configuration of the transportformats is completely controlled by the RAN (Radio Access Network) andsignalled to the MS at call set-up. Correct interpretation of the TF iscrucial at the receiving end as well as the transport format defines theutilized configuration for decoding of the data. When configuring atransport format, the RAN can, for example, choose between a number ofpredefined CRC (Cyclic Redundancy Check) lengths and block lengths.

On transport channels, transport blocks (TB) are exchanged between theMAC sublayer and the physical layer on a transmission time interval(TTI) basis. For each TTI a transport format is chosen and indicatedthrough the transport format indicator (TFIN). In other words, the TFINtells which transport format to use for that particular transport blockon that particular TrCH during that particular TTI. When a transportchannel is inactive, the transport format with a transport block size ofzero (empty transport format) is selected.

Only a limited number of combinations of the transport formats of thedifferent transport channels are allowed. A valid combination is calleda Transport Format Combination (TFC). The set of valid TFCs on a basicphysical subchannel is called a Transport Format Combination Set (TFCS).The TFCS is signalled through Calculated Transport Format Combinations(CTFC).

In order to decode a received sequence the receiver needs to know theactive TFC for the radio packet. This information is transmitted in theTransport Format Combination Identifier (TFCI) field. Aforesaid field isbasically a layer 1 header and has the same function as the stealingbits in GSM. A unique TFCI value is assigned to each of the TFC within aTFCS and upon receipt of a radio packet it is the first element to bedecoded by the receiver. By utilizing the decoded TFCI value thetransport formats for the different transport channels can be determinedand the actual decoding can start.

In case of multislot operation, there shall be one FLO instance for eachbasic physical subchannel. Each FLO instance is configured independentlyby Layer 3 and gets an own TFCS as a result. The number of allocatedbasic physical sub channels depends on the multislot capabilities of theMS.

For the time being the use of FLO is planned to be limited to dedicatedchannels only, thus maintaining the 26-multiframe structure for whichthe SACCH (Slow Associated Control Channel) shall be treated as aseparate logical channel based on GERAN Release 5.

The concept of transport formats and channels as presented in reference[1] is visualized in FIG. 1 where e.g. coded speech is to be transmittedover FLO. Speech is transferred by using three different modes MODE 1,MODE 2, MODE 3 with different bit rates and an additional comfort noisegeneration mode CNG MODE. Inside a mode the speech bits have beendivided into three different classes represented by three transportchannels TrCHA 102, TrCHB 104, and TrCHC 106 on the basis of theirvarying importance during the speech reconstruction stage, for example.Numbers inside the blocks, see e.g. the block pointed by legend 108,being arbitrary in this example though, indicate the required number ofbits in a transport channel and codec mode specific manner. Hence, itcan be noticed from the figure that TrCHA contains four transportformats (0, 60, 40, 30), TrCHB three transport formats (0, 20, 40) andTrCHC only two formats (0, 20). Resulting transport format combinationsTFC1-TFC4, that refer to transport formats on different channels thatcan be active at the same time, are depicted with dotted lines in thefigure. All these valid combinations constitute the TFCS that issignalled through CTFC. An example of CTFC determination is found inreference [1] in addition to techniques applicable in proper TFCselection.

A protocol architecture of FLO in case of Iu mode is depicted in FIG. 2wherein MAC layer 208 maps either a plurality of logical channels orTBFs (temporary block flows) from RLC entities located in RLC layer 206,said RLC layer 206 receiving data from e.g. PDCP 204 (Packet DataConvergence Protocol) and controlled by RRC (Radio Resource Controller)202, to physical layer 210. In current specification [1] logicalchannels are used but are presumably to be replaced with the concept oftemporary block flows in the future. TBF concept is described inreference [3] in more detail. A dedicated channel (DCH) can be used as atransport channel dedicated to one MS in uplink or downlink direction.Three different DCHs have been introduced: CDCH (Control-plane DCH),UDCH (User-plane DCH) and ADCII (Associated DCH), the CDCH and UDCH ofwhich used for transmission of RLC/MAC data transfer blocks, whereas theADCH targeted for transmission of RLC/MAC control blocks. A mobilestation may concurrently have a plurality of transport channels active.

The FLO architecture is illustrated in FIG. 3 especially in relation toLayer 1 for FLO. In this version only a one-step interleaving has beenassumed, i.e. all transport channels on one basic physical subchannelhave the same interleaving depth. An alternative architecture withtwo-step interleaving is disclosed in reference [1] for review. Basicerror detection is carried out with a cyclic redundancy check. ATransport Block is inputted to error detection 302 that utilizes aselected generator polynomial in order to calculate the checksum to beattached to the block. Next, the updated block called Code Block is fedinto a convolutional channel coder 304 introducing additional redundancyto it. In rate matching 306 bits of an Encoded Block are either repeatedor punctured. As the block size can vary, also the number of bits on atransport channel may correspondingly fluctuate. Thereupon, bits shallbe repeated or punctured in order to keep the overall bit rate in linewith the actual allocated bit rate of the corresponding sub-channel.Output from rate matching block 306 is a called a Radio Frame. Transportchannel multiplexing 308 takes care of multiplexing of Radio Frames fromactive transport channels TrCH(i) . . . TrCH(1) received from matchingblock 306 into a CCTrCH (Coded Composite Transport Channel). In TFCImapping 310 a TFCI is constructed for the CCTrCH. The size of the TFCIdepends on the number of TFCs needed. The size should be minimized inorder to avoid unnecessary overhead over the air interface. For example,a TFCI of 3 bits can indicate 8 different transport format combinations.If these are not enough, a dynamic connection reconfiguration is neededto be performed. The TFCI is (block) coded and then interleaved 312 withCCTrCH (these two constituting a Radio Packet) on bursts. The selectedinterleaving technique is configured at call set-up.

RRC layer, Layer 3 for FLO, manages set-up, reconfiguration and releaseof the traffic channels. Upon creating a new connection, Layer 3indicates to the lower layers various parameters to configure thephysical, MAC and RLC layers. Parameters include the transport channelidentity (TrCH Id) and transport format set for each transport channel,transport format combination set through CTFC with modulation parameteretc. In addition, Layer 3 provides transport channel specific parameterssuch as CRC size, rate matching parameters, transport format dynamicattributes etc. The transport channels and the transport formatcombination set are separately configurable in the uplink and downlinkdirections by utilizing e.g. Radio Bearer procedures disclosed insections 7.14.1 and 7.19 of reference [4] in more detail.

Furthermore, Layer 3 may include information about transport formatcombination subset(s) to further restrict the use of transport formatcombinations within the TFCS. Such information may be formed via a“minimum allowed transport format combination index”, an “allowedtransport format combination list”, a “non-allowed transport formationcombination list” etc.

Clearly also incremental TFCS reconfiguration should be possible in FLO,i.e. information only about transport channels or TFCs that are added,modified or deleted could be signalled by e.g. modified Radio Bearersignalling. After various reconfigurations, the overall configurationshould still be consistent, which could be assured by, for example,removing all TFCs from the TFCS that utilize a transport channel to bereleased.

In addition to mere payload data also signalling information istransferred by utilizing the FLO concept. The transmission of signallingdata must be made especially secure as the error scenarios arising frompartially corrupted or completely lost signalling messages may evencorrupt the whole connection if necessary corrective actions are nottaken. Thus both the control plane and RLC/MAC level control messagesshall be transferred with sufficient protection; FLO concept for it'spart enables flexible and dynamic allocation and tuning of transferresources, therefore the protection for signalling may be changed andthe signalling even be multiplexed with outer radio bearers. In GSM, CS1coding has been traditionally used for the protection of signalling.Flexibility offered by the FLO shall, however, not be utilized in thecase of control plane information transfer as it could lead toinconsistent performance throughout the network. Meanwhile, the transferparameters for signalling information shall be kept fixed and in thecase of full rate channels, the first TFC with TFCI=0 is allocatedsolely for signalling transfer with only one active transport channelwith 184 bit transport blocks and 18 bit CRC.

In order to guarantee seamless handovers between full rate and half ratechannels the link level performance of associated signalling must besimilar for the two different channel usage modes. Accordingly, thecoding rate of associated signalling on half rate (HR) channels must beequal to the coding rate of associated signalling on full rate (FR)channels. In GSM/EDGE the interleaving depth of FACCH (Fast AssociatedControl Channel) is increased on half rate channels: it's twice theinterleaving depth of TCH/H. As a result the performance of FACCH/H isvery similar to the performance of FACCH/F; see [5].

However, with the one step interleaving architecture, all TrCHs on onebasic physical subchannel have the same interleaving depth, and the MAClayer shall send the same transport block twice in a row instead of theabove traditional solution. Since coded bits of the same transport blockcan be found in two consecutive radio packets, the effect is as if theinterleaving depth was twice the interleaving used for one radio packet.Two TFCs are defined for sending signalling messages: one is used forthe first transmission and the other for the second transmission. Forthe transport formats used on the transport channel for signalling, anadditional dynamic transport format attribute is required for HRchannels. Layer 3 configures the two TFCs such that, in rate matching,the attribute, parameter R, shall be equal to 0 for the firsttransmission (first radio packet) and equal to 1 for the retransmission(second radio packet); reference [1] discloses further information aboutthe rate matching algorithm. Therefore, two TFCIs with TFCI=0 and TFCI=1are defined for signalling messages on HR channels, each correspondingto one of the two transport formats above. The receiver is able todetermine whether it is a question about receiving the first or thesecond transmission of a signalling block (and therefore apply theappropriate decoding procedures) through the value of the TFCI. Theaforesaid two TFCs shall be configured as in the case of full ratechannels, but the transport formats shall have a different value of theretransmission number parameter R.

Regardless of the above somewhat feasible solution for providingconsistent signalling transfer in different network scenarios andconditions, a number of problems arise especially during a handoverbetween full rate and half rate channels. First, the old TFCS cannot beutilized as such and the TFCS reconfiguration process is an inevitableconsequence thereof. Secondly, if the TFCS has been previouslyconfigured to reserve all the possible TFCs, i.e. the TFCI space is infull use, moving to an HR channel would require adding at least one morebit to the TFCI if possible, rejecting the handover request, or removingone user data TFC in order to provide an additional one for signallingpurposes.

SUMMARY OF THE INVENTION

The object of the present invention is to alleviate the effect of theaforesaid defect in FR⇄HR transitions causing either TFCSreconfiguration, deletion of existing TFCs, or even abortion of thewhole transition procedure in a system utilizing the FLO physical layer.Another object of the invention is to reduce the number of TFCs requiredfor signalling on HR channels.

The object is achieved by aligning the values of parameter R determiningthe retransmission number with the TDMA frame structure, e.g. with framenumbers, during a multiframe comprising a plurality (e.g. 26) frames.The value of R to be used for encoding/decoding data in radio packetscan be then determined on the basis of a preferred rule related to theunderlying existing TDMA frame structure.

The utility of the invention is based on a plurality of issues. As themost obvious one, the value of R does not need to be signalled. Further,as it does not form a part of a transport format anymore, only one TFCis needed for HR channels instead of two TFCs as with the prior artsolution. Still further, the very same TFCS can be used on both FR andHR channels. Due to the time alignment of a receiver with acorresponding transmitter, the receiver is aware of the current value ofparameter R, and by taking the interleaving and transmission delay intoaccount, it can deduct the proper R value for a received packet with.TFCI indicating signalling information embedded therein. The core ideaof the invention may be generalized and utilized in other systems aswell in addition to the GERAN/FLO used herein to mainly concretise thegeneral inventive concept.

According to the invention, a method for transmitting signallinginformation in a TDMA based wireless communications system adapted totransfer data in radio packets over the air interface thereof, a numberof transport blocks included in a radio packet, is characterized in thatit has the steps of

determining the temporal alignment of values for a retransmission numberparameter (R) with the TDMA frame structure, said retransmission numberparameter used for encoding data in a radio packet,

transmitting in a number of first TDMA frames a first radio packetincluding a transport block of signalling information encoded byutilizing a first retransmission number parameter value obtained on thebasis of the temporal alignment information, and

transmitting in a number of second TDMA frames, said second TDMA framesat least partly differing from said first TDMA frames, at least asecond, consecutive radio packet including a transport block ofsignalling information encoded by utilizing a second retransmissionnumber parameter value obtained on the basis of the temporal alignmentinformation.

In another aspect of the invention, a method for receiving signallinginformation in a TDMA based wireless communications system adapted totransfer data in radio packets over the air interface thereof, a numberof transport blocks included in a radio packet, is characterized in thatit has the steps of

determining the temporal alignment of values for a retransmission numberparameter (R) with the TDMA frame structure, said retransmission numberparameter used for encoding data in a radio packet,

receiving in a number of first TDMA frames a first radio packetincluding a transport block of signalling information encoded byutilizing a first retransmission number parameter value obtained on thebasis of the temporal alignment information,

receiving in a number of second TDMA frames, said second TDMA frames atleast partly differing from said first TDMA frames, at least a second,consecutive radio packet including a transport block of signallinginformation encoded by utilizing a second retransmission numberparameter value obtained on the basis of the temporal alignmentinformation, and

decoding the received first radio packet by utilizing said firstretransmission number parameter value and the received second radiopacket by utilizing said second retransmission number parameter value.

In a further aspect of the invention, a device operable in a TDMA basedwireless communications system adapted to transmit data in radio packetsincluding a number of transport blocks, said device comprisingprocessing means and memory means configured to process and storeinstructions and data, and data transfer means configured to transferdata, is characterized in that it is adapted to

determine the temporal alignment of values for a retransmission numberparameter (R) with the TDMA frame structure, said retransmission numberparameter used for encoding data in a radio packet,

transmit in a number of first TDMA frames a first radio packet includinga transport block of signalling information encoded by utilizing a firstretransmission number parameter value obtained on the basis of thetemporal alignment information, and

transmit in a number of second TDMA frames, said second TDMA frames atleast partly differing from said first TDMA frames, at least a second,consecutive radio packet including a transport block of signallinginformation encoded by utilizing a second retransmission numberparameter value obtained on the basis of the temporal alignmentinformation.

Yet in a further aspect, a device operable in a TDMA based wirelesscommunications system adapted to receive data in radio packets includinga number of transport blocks, said device comprising processing meansand memory means configured to process and store instructions and data,and data transfer means configured to transfer data, is characterized inthat it is adapted to

determine the temporal alignment of values for a retransmission numberparameter (R) with the TDMA frame structure, said retransmission numberparameter used for encoding data in a radio packet,

receive in a number of first TDMA frames a first radio packet includinga transport block of signalling information encoded by utilizing a firstretransmission number parameter value obtained on the basis of thetemporal alignment information,

receive in a number of second TDMA frames, said second TDMA frames atleast partly differing from said first TDMA frames, at least a second,consecutive radio packet including a transport block of signallinginformation encoded by utilizing a second retransmission numberparameter value obtained on the basis of the temporal alignmentinformation, and

decode the received first radio packet by utilizing said firstretransmission number parameter value and the received second radiopacket by utilizing said second retransmission number parameter value.

The above term “determining” refers herein to checking the current rulesfor establishing retransmission number parameter values in relation tothe TDMA structure based on e.g. mapping between certain TDMA framenumbers and certain parameter values. The determination phase may inpractise be implemented in a transmitting or receiving device by, forexample, reading and analysing, and optionally updating, a number ofvariables/parameters defining the ruling, such variables/parametersstored in and retrievable from a device memory or received from externaldevices. The determination phase does not however require any change totake place in the already existing mappings.

The term “data” generally refers to signalling and/or payload type data.

In one embodiment of the invention, a network element transmitssignalling information in accordance with the invention to a wirelesscommunications device. Both the network element and the wirelesscommunications device utilize the common rules for temporal alignment ofretransmission number parameter values in relation to the underlyingTDMA structure and thus encode/decode the radio packets with signallinginformation in a mutually compatible manner.

Dependent claims disclose embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Hereinafter the invention is described in more detail by reference tothe attached drawings, wherein

FIG. 1 discloses a visualization of a TFCS structure.

FIG. 2 illustrates FLO protocol architecture in GERAN Iu mode.

FIG. 3 illustrates the FLO architecture.

FIG. 4A is a signalling chart of an embodiment of the invention.

FIG. 4B is a modified signalling chart of an embodiment of theinvention.

FIG. 4C further depicts the scenario of FIG. 4B for transferringsignalling information by utilizing TDMA frame structure as a referencefor determining the proper R parameter values.

FIG. 5 discloses a flow diagram of the method of the invention.

FIG. 6 discloses a block diagram of a device adapted to utilize theinvention.

DETAILED DESCRIPTION OF THE EMBODIMENT OF THE INVENTION

FIGS. 1, 2, and 3 were already discussed in conjunction with thedescription of related prior art.

FIG. 4A discloses, by way of example only, a signalling chart describingthe scenario of one embodiment of the invention in which a wirelesscommunications device such as mobile terminal 402 receives radio packetsfrom network side 404 on a HR channel (only half of the TDMA frames areused for the connection as can be seen from the figure) such as a radioaccess network connected to a core network. The element sending thepackets at the network side may be e.g. a base station. In this example,two radio bursts 406 include the portions of a first radio packet, seedotted side brace, with signalling transport block embedded therein. Theradio packets have been encoded by the network side using aretransmission number parameter R with value 0. The encoding of thepacket internals may refer to e.g rate matching as mentionedhereinbefore. Values of parameter R have in this case been tied to theTDMA frame number of the first bits to be sent for each radio packet.Thus, as the first bits in the first burst have been sent during TDMAframe 0, frame number⇄R value mapping 408 has indicated to use value 0for encoding the whole packet even the last half of the packet wouldhave been sent in another TDMA frame with another R valuecorrespondence, although that was not the case in the current scenario.After receiving both two bursts of the first radio packet, the receivingterminal decodes 412 it on the basis of TFCI indicating signalling TFCand proper R value deducted from the TDMA frame (number) during whichthe first half of the radio packet was transmitted. For encoding theconsecutive, second radio packet with signalling transport block,network 404 utilizes value 1 for R as the transmission of the firstburst containing a portion of the second radio packet occurs in TDMAframe 4 mapped to R value 1.

Accordingly, terminal 402 receives and decodes 414 the both burstscontaining parts of the second radio packet on the basis of the TDMAframe number related to the transmission of the first bits of thepacket. In this figure only two values have been allocated for use withR parameter, namely 0 and 1, but in theory also more than oneretransmission of transport blocks with signalling information ispossible and correspondingly, the mapping between TDMA frame structureand R values could be more versatile as described below. Thetransmission could also occur respectively in the opposite direction,just to be mentioned.

Considering a typical GSM multiframe with 26 frames, each of whichcorresponding to a 5 ms period, the value for parameter R could bedefined as in following table 1. TABLE 1 TDMA frame structure

R value mappings TDMA frame number Value of R 0, 1, 2, 3 0 4, 5, 6, 7 18, 9, 10, 11 0 13, 14, 15, 16 1 17, 18, 19, 20 0 21, 22, 23, 24 1

One should remember that frames 12/25 are reserved forcontrol/supervisory signals transmitted on the SACCH (Slow AssociatedControl Channel) and are thus not available for this purpose.

The value of R to be used by the encoder is given by the TDMA framenumber of the first bits to be transmitted for that radio packet. Forinstance, if the first coded bits of the signalling radio packet aresent on TDMA frame 0, the value of R to be used by the encoder is 0. Ifthe first coded bits are sent on TDMA frame 4, the value of R to be usedis 1. Because radio packets correspond to a 20 ms period, one can easilycheck that two consecutive radio packets never use the same value of R.When bits are received, the decoder knows the TDMA frame number of thefirst bits that were transmitted and can therefore tell which value of Rwas used.

After all, the above example is simplified, as it does not contain, foxexample, possible acknowledgments transmitted by terminal 402 to networkside 404 as a response to the (properly) received packets. In addition,interleaving of radio packets, which typically slightly modifies thescenario, is not shown; see the scenario of FIG. 4B for furtherclarification.

For example, in the GSM system so-called diagonal interleaving is usedfor protecting the bits during transmission. A radio burst includes datafrom the previous radio packet as well in addition to the currentpacket. Now, if one burst is lost during the transmission due to e.g.temporary disturbances on the radio path, the receiver may at leastestimate the contents thereof of the basis of surrounding burstshopefully received without problems. As the transmitted data istypically convolutionally encoded, there exists useful inherentredundancy in it.

Due to the applied diagonal interleaving, one radio packet is nowtransmitted in four consecutive bursts each of which including portionsof two consecutive radio packets as shown in the figure by referencesign 428. To refer an existing real-life situation with FLO and GERANtechnologies, the bursts are transmitted on half rate channel number 0pursuant to [2], for example. The first radio packet carrying signallingis sent on TDMA frames numbered 0, 2, 4, 6 (R=0 was used for encoding)in bursts 422, 423, 424, and 425 whereas the second radio packet is senton TDMA frames numbered 4, 6, 8, 10 (R=1 was used for encoding) inbursts 424, 425, 426, and 427. Thus, the outermost bursts 422, 423 and426, 427 contain also some additional data being however not relevantfrom the invention's standpoint. After receiving the last coded bits ofthe first radio packet in TDMA frame 6, the receiver can decode 430 thefirst signalling radio packet, knowing exactly which value of R was used. Similarly, after receiving the last coded bits of the second radiopacket on TDMA frame 10, the receiver can decode 432 the secondsignalling radio packet with another value for R. Mutual ordering ofpacket portions within the bursts does not have a special meaning in thefigure.

FIG. 4C discloses an alternative view to the scenario of FIG. 4B fromGSM/GERAN standpoint. Exactly half of all the frames in a 26-framemultiframe are shown. A TDMA frame is basically sent every 4.616 ms (Ll)corresponding to a period of 5 ms (L2). Two half-rate channels withtemporal separation are shown in the figure (H#0 and H#l) with framesallocated thereto. In this case channel 0 is selected for transmission.Values of parameter R change every four frames, and thus the consecutivepackets always utilize different R values due to the predetermined andcleverly constructed TDMA frame structure⇄R value mappings. Basicphysical subchannel/time slots within TDMA frames are not depicted inthe figure for clarity. X denotes irrelevant data while referencenumerals 1 and 2 refer to corresponding first and second packets (orpacket portions to be exact) in the radio bursts on two rows describingthe transmission of bursts (H#0 transmit).

Additionally if more than two values of R parameter are needed, thealignment rule can easily be extended as presented in table 2 where Rmaxrefers to the maximum number of retransmissions allowed: TABLE 2 TDMAframe structure <-> R value mappings (R = {0, 1, . . . , Rmax − 1}) TDMAframe number Value of R 0, 1, 2, 3 0 mod R_(max) 4, 5, 6, 7 1 modR_(max) 8, 9, 10, 11 2 mod R_(max) 13, 14, 15, 16 3 mod R_(max) 17, 18,19, 20 4 mod R_(max) 21, 22, 23, 24 5 mod R_(max)

Further supplementary or alternative alignment rules are, of course,possible as long as both transmission ends know and use the same rule:for instance, the value of R to be used by the encoder is given by theTDMA frame number of the first bits to be received.

FIG. 5 discloses a flow diagram of the method of the invention. The pathon the left represents the actions taken at the sending end whereas thepath on the right refers to the receiving side. At method start-up 502 adevice, by referring to a network entity (e.g. a base station) or to awireless communications device like a mobile terminal may, for example,load the software performing the method of the invention to the memorythereof and start execution. In addition, necessary memory areas can beinitialised and communication connections established. Respectively, aneed for sending/receiving signalling information is established totrigger the further execution of the method.

In step 504 the device determines by, for example, retrieving a numberof variables/parameters stored in the memory and analysing themaccording to a programmed logic (e.g. Tables 1 and 2) the currenttemporal alignment of values for parameter R with the TDMA framestructure like TDMA frame numbers. It is also possible to receive newalignment rules from external sources, e.g. BSC or even the far-enddevice, dynamically.

In step 506 the sending device selects a proper value of R for encoding,by which it is referred to, for example, rate matching, radio packetinternals including the transfer block with signalling information. Theselection is based on the available information, see previous step 504,about the TDMA⇄R frame structure alignment rules. For example, TDMAframe number of the first bits of the signalling radio packet to be sentcan be used to define the proper value for R if such a simple mapping ispreferred over more complex ones. In step 508 the radio packet isconstructed normally depending on the system, e.g. according to the FLOarchitecture represented by FIG. 3, and using a proper value for R.Construction stage may include interleaving step already described abovewith necessary buffering in order to combine subsequent packets' dataetc. In phase 510 it is checked whether a re-transmission is neededbased on the number of different R values and if that's the case, steps506 and 508 are repeated until no more retransmissions are left to besent. The flow diagram does not contain any optional informationexchange between the sending and receiving devices, although e.g.acknowledgement messages may be transferred during the execution of themethod. The method is ended in step 512.

At the receiver, in step 514 the alignment rules for parameter R arerespectively determined to properly decode the incoming signallinginformation. In step 516 a radio packet with signalling data is receivedand in step 518 decoded according to a proper R value. Receipt of radiopackets is continued 520 if more of them should be on the way accordingto the current number of retransmissions used. The method is ended instep 512.

It's obvious to a person skilled in the art that the steps presented inFIG. 5 can be modified in order to match the desired use case in a bestpossible way. For example determination steps 504 and 514 may beembedded into R value definition 506 and packet decoding 518 steps ifpreferred as long as proper R value for a radio packet is solved beforeusing any guesstimate for encoding/decoding it. Correspondingly, step ofdecoding radio packet(s) 518 may be performed after receiving aplurality of them, not necessarily after each packet (one at a time).

FIG. 6 depicts one option for basic components of a device like anetwork element, e.g. base station (or a combination of separateelements), or a mobile terminal capable of processing and transferringdata in accordance with the invention. Wording “mobile terminal” refersto, in addition to contemporary cellular phones, also to moresophisticated multimedia terminals, hand held and laptop computers etccapable of wireless communication. Memory 604, divided between one ormore physical memory chips, comprises necessary code 614, e.g. in a formof a computer program/application, and configuration (TDMA framestructure⇄R value relationships) data 612. Processing unit 602 isrequired for the actual execution of the method in accordance withinstructions in code 614. Display 606 and keypad 610 are optionalcomponents often found useful for providing necessary device control anddata visualization means (˜user interface) to the user of the device.Data transfer means 608, e.g. a radio transceiver, are required forhandling data exchange, for example, receipt of configuration data fromother devices and/or transmission/receipt of signalling data to/fromother devices. Code 614 for the execution of the proposed method can bestored and delivered on a carrier medium like a floppy, a CD or a memorycard.

The scope of the invention can be found in the following claims.However, utilized devices, method steps, data structures etc may varydepending on the current scenario, still converging to the basic ideasof this invention. The invention was described by keeping especiallyGERAN/FLO concept in mind but the overall concept could be utilized inother systems bearing the TDMA nature as well.

REFERENCES

[1] 3GPP TR 45.902 V6.4.0 Technical Specification Group GSM/EDGE, RadioAccess Network; Flexible Layer One (Rel 6)

[2] 3GPP TS 45.002 V6.5.0 Technical Specification Group GSM/EDGE, RadioAccess Network; Multiplexing and multiple access on the radio path (Rel6)

[3] 3GPP TS 44.160 V6.3.0 Technical Specification Group GSM/EDGE,General Packet Radio Service (GPRS); Mobile Station (MS)-Base StationSystem (BSS) interface; Radio Link Control/Medium Access Control(RLC/MAC) protocol Iu mode (Rel 6)

[4] 3GPP TS 44.118 V6. 1.0 Technical Specification Group GSM/EDGE, RadioAccess Network; Mobile radio interface layer 3 specification; RadioResource Control (RRC) protocol Iu Mode (Rel 5)

[5] 3GPP TS 45.003 V6.2.0 Technical Specification Group GSM/EDGE, RadioAccess Network; Channel coding (Rel 6)

1. A method for transmitting signalling information in a TDMA based wireless communications system adapted to transfer data in radio packets over the air interface thereof, a number of transport blocks included in a radio packet, characterized in that it has the steps of determining the temporal alignment of values for a retransmission number parameter (R) with the TDMA frame structure, said retransmission number parameter used for encoding data in a radio packet, transmitting in a number of first TDMA frames a first radio packet including a transport block of signalling information encoded by utilizing a first retransmission number parameter value obtained on the basis of the temporal alignment information, and transmitting in a number of second TDMA frames, said second TDMA frames at least partly differing from said first TDMA frames, at least a second, consecutive radio packet including a transport block of signalling information encoded by utilizing a second retransmission number parameter value obtained on the basis of the temporal alignment information.
 2. The method of claim 1, wherein said first and second TDMA frames are transmitted on half-rate channels.
 3. The method of claim 1, wherein the system utilizes the flexible layer one (FLO) for data transfer.
 4. The method of claim 1, wherein the system utilizes GERAN (GSM/EDGE Radio Access Network) as a radio access network.
 5. The method of claim 1, wherein said determining is performed by checking the mapping between TDMA frame numbers and values of the retransmission number parameter (R).
 6. The method of claim 5, wherein a number of frames have been associated with retransmission number parameter value 0 and a number of frames with retransmission number parameter value
 1. 7. The method of claim 6, wherein the mapping for a multiframe including 26 frames indicates value 0 for the retransmission number parameter (R) in the case of frames numbered 0, 1, 2, 3, 8, 9, 10, 11, 17, 18, 19, 20, and value 1 in the case of frames numbered 4, 5, 6, 7, 13, 14, 15, 16, 21, 22, 23, 24, while the multiframe comprises frames numbered from 0 to
 25. 8. The method of claim 5, wherein the mapping for a multiframe comprises division of frames in the multiframe into a plurality of frame groups each of which including a number of consequent frames, and associating each group with a certain retransmission number parameter value.
 9. The method of claim 8, wherein the groups have equal number of frames included.
 10. The method of claim 1, wherein one radio packet is transmitted in four radio bursts, each burst comprising a data portion from at least two radio packets.
 11. The method of claim 1, wherein rules for the temporal alignment are received from or transmitted to another device by the device performing the method.
 12. A method for receiving signalling information in a TDMA based wireless communications system adapted to transfer data in radio packets over the air interface thereof, a number of transport blocks included in a radio packet, characterized in that it has the steps of determining the temporal alignment of values for a retransmission number parameter (R) with the TDMA frame structure, said retransmission number parameter used for encoding data in a radio packet, receiving in a number of first TDMA frames a first radio packet including a transport block of signalling information encoded by utilizing a first retransmission number parameter value obtained on the basis of the temporal alignment information, receiving in a number of second TDMA frames, said second TDMA frames at least partly differing from said first TDMA frames, at least a second, consecutive radio packet including a transport block of signalling information encoded by utilizing a second retransmission number parameter value obtained on the basis of the temporal alignment information, and decoding the received first radio packet by utilizing said first retransmission number parameter value and the received second radio packet by utilizing said second retransmission number parameter value.
 13. The method of claim 12, wherein said first and second TDMA frames are received on half-rate channels.
 14. The method of claim 12, wherein the system utilizes the flexible layer one (FLO) for data transfer.
 15. The method of claim 12, wherein the system utilizes GERAN (GSM/EDGE Radio Access Network) as a radio access network.
 16. The method of claim 12, wherein said determining is performed by checking the mapping between TDMA frame numbers and values of the retransmission number parameter (R).
 17. The method of claim 12, wherein a number of frames have been associated with a retransmission number parameter value 0 and a number of frames with a retransmission number parameter value
 1. 18. The method of claim 12, wherein one radio packet is transmitted in four radio bursts, each burst comprising a data portion from at least two radio packets.
 19. The method of claim 12, wherein rules for the temporal alignment are received from or transmitted to another device by the device performing the method.
 20. A device operable in a TDMA based wireless communications system adapted to transmit data in radio packets including a number of transport blocks, said device comprising processing means and memory means configured to process and store instructions and data, and data transfer means configured to transfer data, characterized in that it is adapted to determine the temporal alignment of values for a retransmission number parameter (R) with the TDMA frame structure, said retransmission number parameter used for encoding data in a radio packet, transmit in a number of first TDMA frames a first radio packet including a transport block of signalling information encoded by utilizing a first retransmission number parameter value obtained on the basis of the temporal alignment information, and transmit in a number of second TDMA frames, said second TDMA frames at least partly differing from said first TDMA frames, at least a second, consecutive radio packet including a transport block of signalling information encoded by utilizing a second retransmission number parameter value obtained on the basis of the temporal alignment information.
 21. The device of claim 20, wherein said first and second TDMA frames are transmitted on half-rate channels.
 22. The device of claim 20, wherein the system utilizes the flexible layer one (FLO) for data transfer.
 23. The device of claim 20, wherein the system utilizes GERAN (GSM/EDGE Radio Access Network) as a radio access network.
 24. The device of claim 20, wherein the temporal alignment is determined through mapping between TDMA frame numbers and values of the retransmission number parameter (R).
 25. The device of claim 24, wherein a number of frames have been associated with retransmission number parameter value 0 and a number of frames with retransmission number parameter value
 1. 26. The device of claim 24, wherein the mapping for a multiframe including 26 frames indicates value 0 for the retransmission number parameter (R) in the case of frames numbered 0, 1, 2, 3, 8, 9, 10, 11, 17, 18, 19, 20, and value 1 in the case of frames numbered 4, 5, 6, 7, 13, 14, 15, 16, 21, 22, 23, 24, while the multiframe comprises frames numbered from 0 to
 25. 27. The device of claim 24, wherein the mapping for a multiframe comprises division of frames in the multiframe into a plurality of frame groups including a number of consequent frames and associating each group with a certain retransmission parameter value.
 28. The device of claim 27, wherein the groups have equal number of frames included.
 29. The device of claim 20, adapted to transmit a radio packet in four radio bursts, each burst comprising data from at least two radio packets.
 30. The device of claim 20, adapted to receive rules for the temporal alignment from another device or to transmit rules for the temporal alignment to another device.
 31. The device of claim 20 that is substantially a mobile terminal or a base station.
 32. The device of claim 20 that is substantially a GSM terminal.
 33. A device operable in a TDMA based wireless communications system adapted to receive data in radio packets including a number of transport blocks, said device comprising processing means and memory means configured to process and store instructions and data, and data transfer means configured to transfer data, characterized in that it is adapted to determine the temporal alignment of values for a retransmission number parameter (R) with the TDMA frame structure, said retransmission number parameter used for encoding data in a radio packet, receive in a number of first TDMA frames a first radio packet including a transport block of signalling information encoded by utilizing a first retransmission number parameter value obtained on the basis of the temporal alignment information, receive in a number of second TDMA frames, said second TDMA frames at least partly differing from said first TDMA frames, at least a second, consecutive radio packet including a transport block of signalling information encoded by utilizing a second retransmission number parameter value obtained on the basis of the temporal alignment information, and decode the received first radio packet by utilizing said first retransmission number parameter value and the received second radio packet by utilizing said second retransmission number parameter value.
 34. The device of claim 33 that is substantially a mobile terminal or a base station.
 35. The device of claim 33 that is operable in GERAN (GSM/EDGE Radio Access Network) radio access network.
 36. The carrier medium carrying the computer program of claim
 36. 37. The computer executable program adapted to execute the steps of claim
 1. 38. The computer executable program adapted to execute the steps of claim
 12. 